UNH Scientist Leads Team
to Greenland to Probe a Piece of Earth's Climate Puzzle
Contact: David Sims
603-862-5369
Science Writer
Institute for the Study of Earth, Oceans, and Space

March 10, 2004

DURHAM, N.H. -- In the summer of 1998, a team of scientists led
by Jack Dibb of the University of New Hampshire was measuring levels
of nitrogen oxides above the permanent snowfields at Summit, Greenland.
The researchers expected to find only small amounts of these gases,
which, among other things, play an important role in the formation
of ground ozone or smog. But readings taken eight meters (26 feet)
above the snow were surprisingly high, with readings taken closer
to the snow surface even higher. “Finally,” recalls
Dibb, “we stuck the inlet right into the snow and the numbers
were astronomical.”

This discovery, and a similar, serendipitous find by a different
team at the South Pole later that same year, opened up a new avenue
of scientific inquiry. Dibb, an atmospheric chemist at UNH’s
Institute for the Study of Earth, Oceans, and Space (EOS), is returning
to Summit as the vernal equinox approaches to dig further into
the mystery, which begins, he surmises, when sunlight hits the
surface of the snow and “photolyzes” impurities in
the snow pack. Some of the reactive compounds produced are thereby
made available to circulate and participate in atmospheric processes.

Of the research Dibb says, “This is a recently recognized
field of tropospheric chemistry. The whole issue of a lot of reactive
gases pouring out of the snow into the atmosphere wasn’t
even on anybody’s radar screen before the late ‘90s.
The thinking was that when it rained or snowed these reactive gases
were taken out of the atmosphere and that was the end of the story.”
But the story is being rewritten, and this has significant implications
for, among other things, understanding ice core records and just
how accurately they provide insight into Earth’s past climate. “Based
on what we’ve discovered,
obviously, when stuff hits the snow it doesn’t just sit there,
it starts getting chewed up by photochemical reactions, or new
compounds that weren’t
even in the atmosphere at the time get formed. This makes it more
difficult to invert ice core records for some chemical species,” Dibb
says.

In addition, since this newly discovered source of reactive gases
is not plugged into current climate models, those simulations,
used for understanding past climate as well as predicting what
may lie ahead, are incomplete at best. Says Dibb, “If you
have this large area source of reactive chemicals that isn’t
considered in any current understanding of the functioning of the
troposphere, models may be getting the ‘right’ answers
for the wrong reasons.”

At Summit, Dibb and 12 other researchers from Georgia Tech, UC
Irvine, UC Davis, the University of Arizona, the National Center
for Atmospheric Research, the Cold Regions Research and Engineering
Laboratory, and NASA, will measure these gases at a time when the
frozen landscape begins to emerge from months of perpetual darkness.
They will work at Summit from mid-March, when the average daytime
temperature will be minus 45 degrees Celsius (-49 Fahrenheit),
to early May.

Says Dibb, who specializes in the chemistry of air-snow exchange, “Ideally,
in a scientific sense, we would be there now – really catching
time when it is dark and then seeing the sun come back. But logistically
and probably even physically, I’m not sure we could make
all these instruments work at minus 70 or 80 C.”

While Dibb has been going to the scientific research facility at
Summit annually since 1989, with funding from the National Science
Foundation, this is the first time a large contingent of researchers
will operate in such extreme conditions in an effort to make measurements
at the site. Adds the scientist, “If we’re not including
this widespread nitrogen oxide source then there’s a hole
in understanding how the atmosphere is functioning. It may be that
this is not important on a global scale, but we need to understand
whether this flux of reactive chemicals out of the snow really
matters.”